Generally the die-casting apparatus will comprise a casting die provided with a cluster of cavities in which individual articles of zinc or magnesium are to be cast, a sprue or feeder passage for delivering the molten metal to the cavity cluster, and a die-casting machine which delivers the molten metal under pressure to the die. Along the path of the molten metal, a tubular nozzle body is provided for conveying the molten metal (zinc or magnesium) to the cluster of cavities.
To avoid cooling of the flow of material in this nozzle body below the minimum permissible temperature for die casting, it has been proposed to heat the nozzle body.
For this purpose, within the nozzle body tubular heating cartridges can be inserted. The heating cartridges extend generally parallel to the flow passage through the nozzle body.
This apparatus has been found to be relatively expensive since the nozzle body must be assembled from a plurality of parts to allow the tubular heating element to be inserted into the nozzle body and the nozzle body must be reassembled after replacement. The joints between the parts frequently pose problems, the construction of the nozzle body often requires substantially transverse dimensions thereof, and the disassembly of the assembly is time-consuming and labor-consuming as far as maintenance is concerned.
The large transverse dimensions of the nozzle body are a reason why the nozzle body cannot be brought close to the cluster of die cavities in the casting die but must be spaced relatively far from its cluster. As a consequence, the amount of material filling the extended sprue which is required to cover this distance may be considerable. The result is that the casting process involves the formation of large quantities of lost material which may have to be remelted later but, for any particular casting operation, is not available.